This invention relates to the removal of solids from aqueous pulp-and-paper mill streams by treating such streams with a waste derived in the nitric acid etching of aluminum foil for capacitor electrodes.
More particularly it relates to the treating of the aqueous pulp-and-paper waste streams with a waste consisting essentially of aqueous aluminum nitrate to which a polyelectrolyte has been added which acts synergistically to improve flocculation, settling, and dosage rates and decolorization.
It has become necessary to treat waste water for solids and color removal, among other things, before discharge. As requirements have become more stringent, it has become more difficult to provide for such treatment economically.
Increasingly, more attention is being paid to resource recovery from waste streams including the use of a waste from one process to treat another waste stream to neutralize or precipitate material from one or both of them, thus reducing the quantity of neutralizing and/or precipitating agents needed. In the case of precipitation, it is quite desirable that the solids be quite dense so they occupy as small a volume as possible to minimize the size of the necessary sludge beds.